Coastal Wetland Trends in the Narragansett Bay Estuary During the 20th Century November 2004 A National Wetlands Inventory Cooperative Interagency Report Coastal Wetland Trends in the Narragansett Bay Estuary During the 20th Century Ralph W. Tiner1, Irene J. Huber2, Todd Nuerminger2, and Aimée L. Mandeville3 1U.S. Fish & Wildlife Service National Wetlands Inventory Program Northeast Region 300 Westgate Center Drive Hadley, MA 01035 2Natural Resources Assessment Group Department of Plant and Soil Sciences University of Massachusetts Stockbridge Hall Amherst, MA 01003 3Department of Natural Resources Science Environmental Data Center University of Rhode Island 1 Greenhouse Road, Room 105 Kingston, RI 02881 November 2004 National Wetlands Inventory Cooperative Interagency Report between U.S. Fish & Wildlife Service, University of Massachusetts-Amherst, University of Rhode Island, and Rhode Island Department of Environmental Management This report should be cited as: Tiner, R.W., I.J. Huber, T. Nuerminger, and A.L. Mandeville. 2004. Coastal Wetland Trends in the Narragansett Bay Estuary During the 20th Century. U.S. Fish and Wildlife Service, Northeast Region, Hadley, MA. In cooperation with the University of Massachusetts-Amherst and the University of Rhode Island. National Wetlands Inventory Cooperative Interagency Report. 37 pp. plus appendices. Table of Contents Page Introduction 1 Study Area 1 Methods 5 Data Compilation 5 Geospatial Database Construction and GIS Analysis 8 Results 9 Baywide 1996 Status 9 Coastal Wetlands and Waters 9 500-foot Buffer Zone 9 Baywide Trends 1951/2 to 1996 15 Coastal Wetland Trends 15 500-foot Buffer Zone Around Coastal Wetlands 15 Trends for Pilot Study Areas 25 Conclusions 35 Acknowledgments 36 References 37 Appendices A. Baywide Summary Tables for the Narragansett Bay Estuary B. Summary Tables for Individual Study Areas List of Tables No. Page 1. Aerial photography used for this study. 6 2. Causes of wetland losses, gains, and changes in type. 7 3. 1996 status of coastal wetlands and waters in the Narragansett bay Estuary. 10 4. Extent of altered coastal wetlands for the Narragansett Bay Estuary in 1996. 13 5. Land use/cover in the 500-foot buffer around coastal wetlands in the Narragansett Bay Estuary in 1996. 14 6. Trends in coastal wetlands and waters in the Narragansett Bay Estuary from the 1950s to the 1990s. 16 7. Nature and causes of coastal wetland changes in the Narragansett Bay Estuary from the 1950s to the 1990s. 19 8. Land use/cover changes in the 500-foot buffer surrounding tidal wetlands in the Narragansett Bay Estuary from the 1950s to the 1990s. 23 9. Status and trends in coastal wetlands for specific study areas. 27 10. Nature and causes of coastal wetland and deepwater habitat trends for Allins Cove. 29 11. Nature and causes of coastal wetland and deepwater habitat trends for Calf Pasture Point. 30 12. Nature and causes of coastal wetland and deepwater habitat trends for Jacobs Point. 31 13. Nature and causes of coastal wetland and deepwater habitat trends for Palmer River. 32 14. Nature and causes of coastal wetland and deepwater habitat trends for Sachuset Point. 33 15. Nature and causes of coastal wetland and deepwater habitat trends for Wesquage Pond. 34 Tables in Appendix A:. 1-A. Changes in estuarine emergent wetlands in the Narragansett Bay Estuary: 1950s to 1990s. 2-A. Changes in estuarine scrub-shrub wetlands in the Narragansett Bay Estuary: 1950s to 1990s. 3-A. Changes in estuarine unconsolidated shores in the Narragansett Bay Estuary: 1950s to 1990s. 4-A. Changes in vegetated coastal wetlands in the Narragansett Bay Estuary: 1950s to 1990s. 5-A. Changes in nonvegetated coastal wetlands in the Narragansett Bay Estuary: 1950s to 1990s. List of Tables (continued) Tables in Appendix B: 1-B. Trends in estuarine wetlands for Allins Cove from the 1930s to the 1950s and from the 1950s to the 1990s. 2-B. Trends in estuarine wetlands for Calf Pasture Point from the 1930s to the 1950s and from the 1950s to the 1990s. 3-B. Trends in estuarine wetlands for Jacobs Point from the 1930s to the 1950s and from the 1950s to the 1990s. 4-B. Trends in estuarine wetlands for Palmer River from the 1930s to the 1950s and from the 1950s to the 1990s. 5-B. Trends in estuarine wetlands for Sachuest Point from the 1930s to the 1950s and from the 1950s to the 1990s. 6-B. Trends in estuarine wetlands for Wesquage Pond from the 1930s to the 1950s and from the 1950s to the 1990s. List of Figures No. Page 1. Location of the Narragansett Bay Estuary and its drainage area. 2 2. Limits of the Narragansett Bay Estuary as defined for this study. 3 3. Location of six pilot areas within the Narragansett Bay Estuary. 4 4. Percent loss of estuarine emergent wetland in the Narragansett Bay Estuary. 21 5. Percent gain in estuarine emergent wetland in the Narragansett Bay Estuary. 21 6. Percent change in estuarine scrub-shrub wetland in the Narragansett Bay Estuary. 22 7. Percent change in estuarine unconsolidated shore in the Narragansett Bay Estuary. 22 Introduction The Rhode Island Department of Environmental Management's Narragansett Bay Estuary Program's (NBEP) goal is to protect and preserve Narragansett Bay through conserving and restoring natural resources and enhancing water quality. NBEP accomplishes this through a variety of projects, including interagency partnerships and community involvement. To manage these valuable resources, NBEP wanted baseline information on coastal wetlands and their buffers. With the aid of the University of Massachusett (UMass), University of Rhode Island (URI), and the U.S. Fish and Wildlife Service (FWS), NBEP obtained an inventory of current coastal wetlands, the 500-foot buffer zone, and potential wetland restoration sites for the estuary. While knowing the current state of these resources is vital to managing the resource, an analysis of trends in these resources would help identify threats and put the presentday resources in a historic context. In 1999, the NBEP and the FWS modified an existing cooperative agreement to produce wetland trends information for the Narragansett Bay Estuary. The FWS works in partnership with UMass (Department of Plant and Soil Sciences, Natural Resources Assessment Group - NRAG) to conduct wetland mapping, trend analysis, and other studies requiring interpretation of aerial photography. NBEP also has an agreement with the URI to perform the geographic information system (GIS) services. URI also played a major role in this project by providing these services. The NBEP will use the results of this work to help develop a coastal wetland conservation and restoration strategy for the Narragansett Bay Estuary. This report presents the results of this multi-agency cooperative project. It summarizes data for the entire estuary and for several pilot study areas where trends were analyzed back to the 1930s. Study Area The Narragansett Bay Estuary is a 147-square mile coastal embayment (including Mount Hope Bay) that dominates the Rhode Island landscape (Figures 1 and 2). It is the receiving basin for seven major watersheds in Rhode Island and Massachusetts including the Blackstone, Moshassuck, Pawtuxet, Taunton, Ten Mile, Warren, and Woonaquatucket. The Estuary is defined by the limits of brackish tidal water and hydrogeomorphology. The baywide coastal wetlands trends analysis (1950s-1990s) was limited to the Rhode Island portion. Within the Narragansett Bay Estuary, six areas were selected as pilot areas to examine wetland trends from the 1930s-1950s in addition to the 1950s-1990s analysis done baywide: 1) Allins Cove, 2) Calf Pasture Point, 3) Jacobs Point, 4) Palmer River, 5) Sachuest Point, and 6) Wesquage Pond (Figure 3). 1 Figure 1. Location of the Narragansett Bay Estuary and its drainage area; the general boundary of the estuary is the dark gray-shaded area. 2 Figure 2. Limits of the Narragansett Bay Estuary as defined for this study. 3 Figure 3. Location of six pilot areas within the Narragansett Bay Estuary. 4 Methods Data Compiliation Conventional photointerpretation techniques were used to identify trends in coastal wetlands and the 500-buffer around these wetlands. For the Narragansett Bay study area, trends from the 1950s to the 1990s were determined. For the six pilot study areas (Allins Cove, Calf Pasture Point, Jacobs Point, Palmer River, Sachuset Point, and Wesquage Pond), coastal wetland trends were identified for two time periods: the late1930s/early 1940s-1950s and the 1950s-1990s. Table 1 summarizes the aerial photography used for the study. Photointerpretation was performed using mirror stereoscopes. Wetlands and deepwater habitats were classified according to "Classification of Wetlands and Deepwater Habitats of the United States" (Cowardin et al. 1979), the national digital data standard for wetland inventory and reporting on wetland trends. For this study, coastal wetlands include Cowardin's marine and estuarine intertidal wetlands - tidal wetlands with measurable traces of ocean-derived salts. Wetland changes to and from nonwetlands were categorized according to the features presented in Table 2. These features represent modifications of the Anderson et al. (1976) national land use/cover classification system. Multiple codes may be assigned to a change in a given wetland. Wetland trends were marked on acetate overlays attached to aerial photographs. Changes in wetlands and deepwater habitats were interpreted using Bausch & Lomb stereo integration scopes. Land use/cover changes in the 500-foot buffer around coastal wetlands were identified using a Bausch & Lomb stereo zoom transfer scope (ZTS) which was also used to match photointerpreted trends data to 1:24,000 frosted mylar maps (prepared by URI). The mylar overlays showing trends were digitized for GIS analysis. The minimum mapping unit for wetland change polygons was 0.25 acre, although smaller polygons of wetland loss were mapped. For more detailed information on methods, see Huber and Nuerminger (2003). 5 Table 1.